Pleuroparenchymal fibroelastosis (PPFE) is a rare interstitial lung disease characterized by predominantly upper lobe fibrosis involving the pleura and subpleural lung parenchyma. PPFE has been classified as either idiopathic or secondary. Idiopathic PPFE (iPPFE) is currently defined as a rare but distinct disease entity in the updated international classification of idiopathic interstitial pneumonias (IIPs) by ATS/ERS, while secondary PPFE is associated with a variety conditions, such as transplantation, dust exposure, autoimmune diseases, and genetic mutations. Although the precise pathogenesis remains unclear, it may represent a pattern of chronic lung injury in response to various stimuli and/or in association with immune dysregulation or genetic factors, such as telomerase-associated genes. Typically, a dry cough and dyspnea are most common symptoms. Patients with PPFE show a “flat chest” with a lean body and restrictive impairments with increased residual volume (RV)/total lung capacity (TLC) on pulmonary function test. Chest x-ray shows bilateral pleural thickening and a parenchymal band in the apical portion. HRCT exhibits bilateral subpleural dense consolidation with traction bronchiectasis and reticulation. 60-90% of patients with iPPFE also have the co-existing lower-lobe interstitial lung disease (ILD). Histologically, markedly dense fibrosis of the pleura and subpleural parenchyma, with an abrupt transition to a normal parenchyma, is found. Subpleural parenchymal fibrosis is characterized by intra-alveolar fibrosis with the prominent deposition of elastic fibers. Although there are no established biomarkers, SP-D and/or KL-6 are likely to be elevated. We previously reported urinary desmosine, which is a degradation product of elastin, as a promising biomarker for the diagnosis of iPPFE. Surgical lung biopsy is essential for a definitive PPFE diagnosis, but it is often difficult because of poor pulmonary function and persistent post-operative pneumothorax. Thus, several clinical diagnostic criteria have recently been proposed. With no effective therapy currently established, its prognosis has remained poor (5-year survival: 30-50%, median survival: 3 years). Regarding prognostic factors, the co-existing lower-lobe ILD, lower FVC, a history of pneumothorax, and male sex have been shown to be significantly associated with a poor prognosis. The radiologic PPFE-like pattern is also observed in ILDs other than PPFE and is related to a poor prognosis. The number of studies on PPFE has markedly increased in the last decade. Therefore, our knowledge on PPFE has significantly expanded. However, there are still many issues that need to be elucidated, including the pathogenesis, pathophysiology, and treatment of PPFE. Future research will clarify these issues.